This invention pertains to creating a magnetic image formed of toner particles having differing sizes. More specifically, it pertains to a method for creating such a magnetic image unit by forming a latent magnetic image having vectors distributed about the perimeter of a magnetizable facial expanse generally parallel to the plane of the expanse, the length of such vectors corresponding with particle fines.
The method of the present invention is particularly suited to be used in an electromagnetic printing system in which an electro-magnetic write head is used to generate latent magnetic images in a planar-like magnetic-image-storage medium having a magnetizable facial expanse. The latent magnetic image is then decorated with a mass of toner particles to form a toner image which is subsequently transferred to a toner-adherable medium, such as paper.
In such a system, as contemplated for use in practicing the instant invention, composite images are generated by placing combinations of individual toner image units in a desired configuration. It is highly desirable in such a system to create toned image units which have well-defined perimeters, so that when they are collectively formed in an overall image it also will have well-defined edges.
It is known in the art that toner tends to be attracted toward flux transitions in a magnetic medium. Conventional imaging, therefore, is typically based on a method of positioning adjacent opposite-flux-directed magnetic image units so that a flux transition is provided at their common boundary. This type of imaging, however, tends to produce inconsistent toning of the image units since a substantial portion of each image unit is not associated with a flux transition, and therefore only attracts limited amounts of toner.
It is therefore a desired object of the present invention to provide a method of creating a controlled-distribution, toned magnetic image unit on a facial expanse of a magnetic-image-storage medium.
In particular, it is an object of the present invention to provide such a method in which a toner population having particles of differing sizes is used to decorate the magnetic image unit such that fines predominate adjacent its outer perimeter.
It is also an object of the present invention to provide such an imaging method which produces a toned image unit having toner particle fines adjacent its perimeter and increasingly coarse particles toward a central region of the image unit.
The preferred method of practicing the instant invention includes the steps of creating in a magnetizable facial expanse a latent magnetic image having a generally circular configuration characterized by radially extending force vectors adjacent the image perimeter which generally lie in the plane of the expanse, the size of such vectors corresponding effectively to particle fines. Force vectors central in the image tend to be oblique relative to the plane of the expanse. This latent image is then decorated with a mass of such particles and by said decorating, and utilizing the forces associated with the radial and oblique vectors, capturing toner particles on the facial expanse extending over the latent image. The toner particle distribution resulting in this method provides for fines captured adjacent the perimeter of the image with increasingly coarse particles captured centrally in the image.
Each toned image unit produced by this method has well-defined edges and is generally completely toned. These and additional objects and advantages of the present invention will be more clearly understood from a consideration of the drawings and the following detailed description of the preferred method of practicing the present invention.